As a hazardous waste, the disposal of chromium enriched tannery sludge has attracted increasing public concern due to its potential adverse risks towards the environment. And incineration is considered to be an effective method to stabilize heavy metals, like Cr, in solid phase during tannery sludge treatment. In this study, real chromium enriched tannery sludge without pre-treatment was incinerated at 300°C-1200 °C under air atmosphere to investigate the transformation of chromium speciation. Here detailed thermal behavior, phase transformation and chromium speciation were characterized by TG-DSC, XRD and XPS, respectively. Experimental results show that content of Cr(VI) increases gradually with the increase of temperature from 300 °C to 500 °C and reaches a maximal level of 46% total Cr at 500 °C, with different Cr(VI) species of CaCrO4, MgCrO4 and Cr5O12. However, the content of Cr(VI) decreases gradually with the further increase of temperature, with only about 5% Cr(VI) at high temperature of 1200 °C, due to formation of Cr(III) species of Cr2O3 crystallite and MgCr2O4 spinel. Besides, a growing number of hexagonally shaped flake-like crystallite Cr2O3 can be discovered from characterization results of XRD and SEM. Finally, the reduction of CaCrO4 to Cr2O3 in the presence of SiO2 is thermodynamically feasible over 700 °C, indicating possible transformation of Cr(VI) to Cr(III) through controlled incineration temperature.

中文翻译：

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大气环境下焚烧温度对真正富铬制革污泥中铬形态的影响。

作为一种危险废物，富含铬的制革厂污泥的处置由于其对环境的潜在不利风险而引起了越来越多的公众关注。并且焚烧被认为是在制革厂污泥处理过程中稳定固相中重金属（如Cr）的有效方法。在这项研究中，未经空气处理的真实富铬制革污泥在空气气氛下于300°C-1200°C焚烧，以研究铬形态的转化。在此，分别通过TG-DSC，XRD和XPS表征了详细的热行为，相变和铬形态。实验结果表明，随着温度的升高，从300°C升高到500°C，Cr（VI）含量逐渐增加，在500°C时，Cr（VI）的含量最高达到46％的总Cr，而不同的Cr（VI）种类的CaCrO4，MgCrO4和Cr5O12。然而，随着温度的进一步升高，Cr（VI）的含量逐渐降低，在1200°C的高温下，只有约5％的Cr（VI），这是由于Cr2O3微晶和MgCr2O4尖晶石形成了Cr（III） 。此外，从XRD和SEM的表征结果中可以发现越来越多的六角形片状微晶Cr2O3。最后，在SiO2存在下将CaCrO4还原为Cr2O3在700°C的热力学上是可行的，这表明通过控制的焚烧温度，Cr（VI）可能转化为Cr（III）。从XRD和SEM的表征结果可以发现，越来越多的六角形片状微晶Cr2O3。最后，在SiO2存在下将CaCrO4还原为Cr2O3在700°C的热力学上是可行的，这表明通过控制的焚烧温度，Cr（VI）可能转化为Cr（III）。从XRD和SEM的表征结果可以发现，越来越多的六角形片状微晶Cr2O3。最后，在SiO2存在下将CaCrO4还原为Cr2O3在700°C的热力学上是可行的，这表明通过控制的焚烧温度，Cr（VI）可能转化为Cr（III）。